Supersensitization of photographic silver halide emulsions



Nov. 18, 1958 J. E. JONES 2,860,982

SUPERSENSITIZATION OF PHOTOGRAPHIC SILVER HALIDE EMULSIONS Filed May 21, 195e E51 v f.

300 400 500 600 700 mjl.

A= 2 3 'DICYANOMETHYLENE l CYCLOHEXEN I"YL) METHYLENE] 3 METHYLBENZOT HIAZOLINE B =2 E( 3DICYNOMETHYLENE CYCLOHEXEN I' YL) METHYLENE] '3' METHYLBENZOTHIAZOLINE WITH PYRIDINE c 2- [(3- DlcYANoMl-:THYLENE -lcYcLoHExl-:N -1- YI.) METHYLENE] 3 METHYLBENzoxAzoLINE D 2 3 DICYANOMETHYLENE ICYCLGHEXEN "l-YL) METHYLENE] BMETHYLBENZOXAZOLINE WITH PYRIDINE 300 400 500 600 700 mju E= 2 [(6 CARBETHOXY 3 'ADICYANOMETHYLENE l CYCLOHEXEN YL) METHYLENE] '3' METHYLBENZOXAZOLINE F= 2 [(Gff CARBETHOXY 3' DICYANOMETHYLENEI'CYCLOHEXEN I' YL) METHYLENE]ZVMETHYLBENZOXAZOLINE WITH PYRIDINE JEAN E. JONES INVENTOR.

ATTORNEYS.

SUPERSENSITIZATION F PHOTOGRAPHIC SILVER`HALIDE EMULSIONS .lean E. Jones, Rochester, N. Y., `a'ssignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application May 21, 1956, Serial No. 586,054

19 Claims. (Cl.96104) This invention relates to photographic #silver halide emulsions containing certain polymethine dyespand in supersensitizing combination therewith, pyridine bases.

It is known in the art of making photographic emulsions that certain -dyes of the cyanine class alter the sensitivity of photographic emulsions lof the gelatinosilver-halide kind, when the dyes are vincorporated in the emulsions. It is also known-.that-the sensitization produced by a given dye varies somewhat withthetype of emulsion vin which the dye is incorporated. -Furthermore, the sensitization of va given emulsion by a given dye may lbe altered by varying the'conditions in the emulsion. For example, the sensitization may be increased by increasing the silver ion concentration Vor decreasing lthe hydrogen ion concentration (i. e., increasing the alkalinity) or both. Thus, -sensitization can be increased by bathing plates, coated with a spectrally sensitized emulsion, in water or in aqueous .solutions of ammonia. Such a process of altering the sensitivity of a sensitized emulsion by increasing the silver Aion concentration and/or by Vdecreasing 'the hydrogen `ionr'concentration is commonly called -hypersensitization. `Hypersensitized emulsions have generally poor ykeeping qualities.

I have now found a new means of .altering the sensitivity in emulsions containing merocyanine dyes. Since the conditions in the emulsion, i. e., the hydrogen ion and/or the silver ion concentration undergo flittle .ortno change in my method, I shall designate my i-new=m'ethod as a kind of supersensitization.

It is, therefore, an object Vof my invention toprovide photographic silver halide emulsions containingk polymethine dyes, and in'supersensitizing combination therewith, pyridine' bases. Another obje'ctfis to kprovide a process for preparing these sensitizedfernulsi'ons Other objects will become apparent ,froma consideration of the following description andl examples.

The polymethine dyes useful'in'practicing my invention can be represented by the following general formula:

wherein R represents l an 'alkyl'.group, such as imethyl, ethyl, propyl, butyl, carbethoxymethyLbenzyl ,(phenylmethyl), etc. (e. g., an alkyl group containing from l to 4 carbon atoms), Vn represents a positive integer of from l to 2, Q represents the non-metallic `atoms-necessary to complete a cyclohexene Aring, and Z represents the non-metallic atoms necessary to complete al heterocyclic nucleus containing from 5 --to 6 atoms in the heterocyclic ring, such as those `selected from the group consisting of those of the benzothazole series` (e. g., benzothiazole, 4-chlorobenzothiazole, V5- chlorobenzothiazole, -chlorobenzothiazole, 7-chlorobenzothiazole, 4- methylbenzothiazole, 5methylbenzothiazole, y-methylbenzothiazole, 5-bromobenzothiazole, ebromobenzothiazole, 4-phenylbenzothiazole, ,Sfphenylbenzothiazole, y4- methoxybenzothiazole, 5-methoxybenzothiazole, ;6.methoxybenzothiazole, 5iodobenzothiazole, 6'.iodol:ienz'othia zone, 4-ethoxybenzothiazole, vS-ethoxybenz'othiazole, tetvrahydrobenzothiazole, 5,-dimethoxybenzothiazole, 25,6-

p 2,860,982 Patented Nov. 1s, 195s "ice dioxymethylenebenzothiazole, 5-hydroxybenzothiazole, 6-` hydroxybenzothiazole, `etc.), those ofthe naphthothiaf zole series (e. g., naphthoilfllthiazole, naphtho[2,1] thiazole, 5.-methoxynaphtho[2,llthiazole, S-ethoxynaphtho[2,l]thiazole, :8methoxynaphthol1,2lthiazole, 7- methoxynaphthoi1,2]thiazole, etc.), thoseof the acenaphtho[l,2lthiazole series (e. g., acenaphthoil-,Zlthiazole, etc.), those of the benzoxazole series (e. g., benzoxazole, 5-chlorobenzoxazole, 5-methylbenzoxavzole, 5- phenylbenzoxazole, "-methylbenzoxazole, *i6-dimethylbenzoxazole, 4,6-dimethylbenzoxazole, 5-methoxybenzoxazole, 5ethoxybenzoxazole, 5-chlorobenzoxazole, 6- rnethoxybenzoxazole, v5-hydroxybenzoxazole, 6-hydroxy- .benzoxazole, etc.), those of the naphthoxazole series (e. g., naphtho[1,2loxazole, naphtho[2,l]oxazole, etc.), those of the benzoselenazole series (e. g., benzoselenazole, 5-chlorobenzoselenazolc, 5methoxybenzoselenazole, 5 hydroxybenzoselenazole, tetrahydrobenzoselenazole, etc.), those of the'naphthoselenazole series (e. g., naphtho[l,2]selenazole, naphtho[2,l]selenazole, etc.), lthose of the thiazoline series' (e. g., thiazoline, 4-methylthiazoline, etc.), those of the benzimidazole series (e. g., 1,3-di; ethylbenzimidazole, l-ethyl-3-phenylbenzimidazole, etc.),I those of the 3,3-dialkylindolenine series (e. g., 3,3-dimethylindolenine, 3,3,5 trimethylindolenine, 3,3,7 trimethylindolenine, etc.), etc.

Especially useful polymethine dyes embraced by Formula I which can be used in my invention comprise the dyes represented by the following general formula:

wherein R4 represents a hydrogen atom or a lower alkyl group, such as methyl, ethyl, etc. Typical bases include pyridine, 1:-, 'and vfy-picoline, etc.

Polymethine dyes selected from those of Formula I which can be used in my invention comprise those represented by the following formulas:

CH3 CH3 2[ (3-dicyanomethylene-5,-dimethyl-l-eyclohexen-l-yl) methylene]-S-methylbenzothiazoline 2-[ (6-carbethoxy-3-dlcyanomethy1ene-1-cyclohexen-l-yl methylene]-3-methy1benzothiazo1ine ene] -3-methylbenzo thiazoline 2- [.3v S-tlicyanomethylene-,-diluethyl-l-cyclohexen-l-yl allylidene]-S-ethylbenzoxazoline 2-[ (3-dicyanomethylene-5,5-dimethy1-1-cyclohexen-l-yl)- methylene]-3-methylbenzose1enazo1ine According to my invention, I incorporate one or more of the polymethne dyes of Formula I with one or more of the pyridine bases of Formula II in a photographic silver halide emulsion. My invention is particularly directed to the ordinarily employed gelatinosilver-halide emulsions. However, my supersensitizing combinations can beemployed in silver halide emulsions in which the carrier is other than gelatin, e. g., a resinous substance or cellulosic material which has no deteriorating effect on thesilver halide.

,My invention is primarily directed to the ordinarily employed gelatno-silver-halide developing-out emulsions, e. g., gelatino-silver-chloride, chlorobromide, -chloroiodide, chlorobromiodide, -bromide and bromiodide developing-out emulsions. While the results in the following examples were obtained using gelatino-silver-bromiodide emulsions, useful results have also been obtained using gelatino-silver-chlorobromide emulsions. Particularly improved sensitizing activity has been obtained in gelatino-silver-bromiodide emulsions of the developingout type. Emulsions which form the latent image mostly inside the silver halide grains, such as the emulsions set forth in U. S. Patent 2,456,956, dated December 2l, 1948, can also be employed in practicing my invention.

The emulsions prepared in accordance with my invention can be coated in the usual manner on any suitable support, e. g., glass, cellulose nitrate lm, cellulose acetate lm, polyvinyl acetal resin film, glycol terephthalate film, polystyrene lm, paper, metal, etc.

The polymethine sensitizing dyes of Formula I or la and pyridine bases of Formula II can be employed in various concentrations, depending upon the effects desired. As is well known in the art, the sensitivity conferred upon an emulsion by a sensitizing dye does not increase proportionately to the concentration of the dye in the emulsion, but rather passes through an optimum as the concentration is increased. In practicing my invention, the individual sensitizing dyes are advantageously employed at approximately their optimum concentration (i. e., the concentration at which the individual dyes give their greatest sensitivity). In general, the pyridine bases represented by Formula II above have little or no sensitizing action on the emulsions.

The optimum concentration of a sensitizing dye can be determined in amanner well known to those skilled in the art by measuring `the sensitivity of a series of test portions o f the same emulsion, each portion containing a different concentration of the sensitizing dye. The optimum concentration of my supersensitizing combinations can, of course, be readily determined in the same manner, by measuring the sensitivity of a series of test portions of the same emulsion, each portion containing aditerent concentration of the sensitizing dye used in the combination. In determining the optimum concentration for" the supersensitizing combination, it is adtion.-l Thezconcentration. of the. 4dyeteari; thenzbef increased until- .the :optimum .fconcentration,.suitablel for.;use;.in the 6 pelyrinylaceti resiirm, paper.. etc...tQ..a.Suit-able .tliikne s sandfallowed to..dry The de tailsof suchyl coating nietliodsarefwell known to those skilledintheart.

The amounts VE offsensitizingzdye and A`pyridinebase actuA combination;,is-determined.'. 5;. ally incorporated in the emu1sion ..will. vary somewhat 4 Ordinarily;.theoptimumorrneangoptiinunnconcentrafrom case to v case, according to lthe emulsion' employed, tionwof.` the@ dyes selected.;-from.;those; represented. byi particular sens itiz ingdyev and pyridine base.emp loyed,1 Formula AI oriIa vabove:which-:Izeruployfinpractising my and accordingto the` eiectdesired. The regiilation` and. invention is :of the .ordeno Horny-@0510.10.30 gram per adoption of the mosteconomical proportions will be apmol.,ofi\ silver; halide :rin tlielemulsiom. 10 parent to those skilled in the art upon making the ordinary Therpyridine.basesselected from those..represented by observations and testscustomarilyemployed in the, art. Formula'II above areadvantageously.employedinaconf. Accordingly, thel foregoingA procedures and ,prop ortions.. centrationsf-on.theaorderfofrom lOaOyto 5.0.,Ojgi1amsf.perr are to be -regarded only.as.illustratiyef Clearlyfmy inmolaofsilverhalide in fthe.emulsione` vention is directed to any emulsion containing a com-` Generallysspeaking. the;.concentration-.of.thel dyeof l5- bination of the aforesaid ,sensitizing dyes. and pyridine Formula1 oi-#Iafto.theipyridinebase of-.Eormulamiican bases, wherebythe emulsion has a speedgreater than vary/rather widely in my.combinations;.e...g., from 1;2A that obtainable with, either type of.ing redient alone. to 1:1000 (by Weight) in many cases. f The following examples will serve to illustrate yfurther Thefmethodssof incorporatingssensitizing;dyesin .ph'othemannerof 'practieiDg-my,IlVeIlODI T0 different PrO- togl'aphicemulsions-, areifweuknown:t@ those'zZOjpOrtiOnS Of the Same batch Of photographic gelatin@- Ithe/.frutta In ipractic'ing Vmy:iriventiongntheisensitizing dyes silver-bromiodide emulsion were addedf(1) a sensitizing carnibe z-di'rectly-:added-1to: the emulsions, ontheyzcanrbe dye selected from .those of Eormula I 01. Ia abOVe and (2) addedztoq-the.femu1sions1in. the..form. of. their solutions. a combinatlonef the SeDStlZIlgdye of Formula I .or I a Advantageousiy, the sensitizing dyes of Formula I Oria.. and a pyrldme base, such aSthOSe renresentedby Forcan. be .dissolved in .arn appropriate solvent,- such vas ace- 25' Hilliad abOVe- N0 data 0n the ,COalDg Contalllillg the tone,.meth'ano1, etc., andzthese solutions added to the pyridine. b aSe OfFOrImllalI alone are giveiLinasmuch photographic emulsions.- Sincethe pyridine ,bases OfFOfas it has been found that these` compounds have. little or muiaziiaare liquids andarencompatible with'- the phon0 measurable. Sensitizing. action of'their Own when so tographic emulsions, .thesensitizing dyes of Formula I or` emPlQl/.ed in heSe emUiSliOliS. While. different emulsion Ia can-frequently berdissolved'v ii1.these,pyridine.bases 30 baCheS Were emPiOYedlD SOmeOf these examples, the and the :resulting solutions added; to the emulsions. Alsame emulsion batches were employed forthe coatings ternatively,zassolution.ofthesensitizingqdyespof Formula.. 111 eah lndlVldUai @Xampief Before CoatingA Qui the I or Ia in a solvent other than the pyridine bases can emUlSlOlS 011' the SUPPQI, thev @13111510118.Containlrlgihe be intermixed with the pyridine bases beforeaddition to addenda were digested fOr a. SIOV 'time in etailk mainthe emulsion, and this .mixture added ein, .theusual. man- 35. tainedatabout 52l C. The differfnt Portionsf emulner. The sensitizing dyes and pyridine bases of my sion Weretherl` COeiedeH. the ySUPPGITS aUdVeXPOSedIl invention are advantageously incorporated in the finished, the S1121 'manner 111 a Speetl'qgrapi? aan@ a. SCHStOmeief washedemulsions and shouldA beuniformlyidistributed (Type Ib), through e flite. 3S Jdel'flfedln the following throughout the emulsions. The following procedure is table.. The30/E speed, gamma aridfogobtamed after satisfactory: Stock solutions of the sensitivzingf dyes de- 40 development 0f heeXPQSed elllllSlODS .are glVeIlbelOW- scrib'ed'labove are prepared Iby dissolving the same-in ap- The deVelOPeI emPlOYed had the fOilOW-illgCOmPOSOHI propriate solvents. Then to the owable, gelatine-silver- G halide emulsion, the desired amounts of the stock solup N.mg/1151121111inophenol.` sulfate 2.0 tion of one or more of these sensitizing dyes is slowly Hydroquinone 8.0 added, while'stirring the. emulsion.4 Stir'ring is continued 45 Sodiumnsul' (mhy'dfws) r l 90 0 until thedye '(or dyes) is thoroughlyincorporated 1n the Sodium CarbonateV monohydrat 52,5 emulsion: Then, the Adesired amount ofthe pyridine base Potassium. bromide A 5 0 is slowly' added to the-emulsion, while stirring.; If'de- Waterfomaka one liter. sired, the pyridine ,base can be addedv prior to the solu- L tion of sensitizing dye (or. dyes), or amixture. Ofthese 50 Wratten No. IZlter transmits substantially no light two ingredients can be added" ina single operation; of Wavelength shonethan ab0uff-495 111111 andfwfatten When the two ingredients are.,separately added, stirring NO- 215 ltef transmts 'Substantlally 110 hht 0f Wave is continued until all ingredientsl have been uniformly lellgihshoftef than-ab0ut-580 m11- dispersed throughout the emulsions. The supersensitized The. i1ierS.-11Sed..1 i1 helexarnples. below were selected` emulsion can then be coated out on a suitable support, 55 SOthat they. ranSmitted. light..lrrtheegioninwhich the. such as glass, ce1lulose. nitrate lm, vcellulose acetate. film, sensitizing. dyes.had,thei r` maximum sensitivity.

Without Base WithBase Dye (g./ Base (cc./ Exposure Example. mol..AgX) inohAgX) Filterv SOIE Gamma. Fog 30E] `Grainma Fog No.

Speed A 1. z 3.60 .0sI 131 3.26 .10 12y f2. .8sY .07 114. 2.86 .07 12, 3: (.0 2.98, .0s 30 3.20 .09. 25` 4. (.08) .60 .10- 3.4 1.00 .12 i2 5. 2.04. ,06. 37- 3.12. .i4 25 6., 3.16 .06 109 3.00 .07 12 7., 3.02-y .06l 109` 2.82 .0sY 12v s. mi .06l 1&5` 2.68 .08., .12 9. nii. .07 3sA 2.86 .i0 25 10. nii .0s 0.25. 1.30 .i1 12 ii. (.0 3.54. .07. 111 3.40` .00. 12. i2. (.0) 2.50 .06 30.0.l 3.26 .08. iiA 13. (.08) do a` f 2;56 .00Vv 16.9. 2:64y .07. 12 7. (.08) a-Pico1me(30). l isti; r5.2l .01: 2 04v 2.4y .08.. 12

7 `In a mannerv similar to that illustrated in the -above table,- other polymethine dyes represented by Formulas I or Ia above `can be Vemployed in combination with various pyridine bases', /such as those represented by Formula II above to advantage.

I have also found that compounds corresponding to can be employed in combination with the pyridine bases p represented by Formula II, such as pyridine. Such derivatives of the compounds of Formulas I or Ia can be obtained from ethylcyanoacetate according to the methods described in U. S. Patent 2,638,473, U. S. Patent 2,697,707 and Belgian Patent 506,549.

The accompanying drawing illustrates the supersensitizing effect obtained with three of my new combinations of polymethine dyes and the pyridine bases in gelatinosilver-bromiodide emulsions. ing is a diagrammatic reproduction of two spectrograms. In each gure, the sensitivity of the emulsion containing only the polymethine dye of Formulas I or Ia is represented by the solid curve. The sensitivity of the emulsion containing both the polymethine dye of'Formulas I or Ia and the pyridine base of Formula II is represented by the curve consisting of short dashes. No curve showing the sensitivity of the emulsion containing the pyridine base of Formula Il is shown, since these compounds have no measurable effect on the emulsions employed.

In Figure 1, curve A represents the sensitivity of an ordinary gelatino-silver-bromiodide emulsion sensitized with 2[ (3-dicyanomethylene-1cyclohexen1yl) methylenelf3-methylbenzothiazoline, while curve B represents the sensitivity of the same emulsion sensitized with 2-[(3 dcyanomethylene- 1cyc1ohexen l-yl -methylenel -3 -methylbenzothiazoline and pyridine. I`he sensitometric measurements for these .emulsions are given in Example 2 of the above table.

In Figure 2, curve C represents the sensitivity of. an ordinary gelatino-silver-bromiodide emulsion sensitized with 2- (3-dicyanomethylene-l-cyclohexen-l-yl methylene]-S-methylbenzoxazoline, while curve D represents the sensitivity of the same emulsion sensitized with 2-[.(3 dicyanomethylene-l-cyclohexen-l-yl)methylene]3meth ylbenzoxazolinc` and pyridine. The sensitometric measurements for these emulsions are given in Example 7 of the above table.

In Figure 3, curve E represents the sensitivity of an ordinary gelatino-silver-bromiodide emulsion sensitized with 2- l (6-carbethoxy-3-dicyanomethylene-1-cyclohexen- 1-yl)methylene]-3-methylbenzoxazoline, while curve F Each figure of the draw-V Cir represents the sensitivity of the same emulsion sensitized g M with 2- 6-carbethoxy-3-dicyanomethylene-1 -cyclohexeni 1 yl)methylene] 3 methylbenzoxazoline and pyridine.4 fj.,

The sensitcmetric measurements for these emulsions are given in Example 9 of the above table.

Photographic silver halide emulsions, such as those n listed above, containing the supersensitizing combinations of my invention can also contain such addenda as chemical sensitizers, e. g., sulfur sensitizers (e. g., allyl thiocarbamide, thiourea, allylisothiocyanate, cystine, etc.), various gold compounds (e. g., potassium chloroaurate, auric trichloride, etc.) (see U. S. Patents 2,540,085;

2,597,856 and 2,597,915), various palladium compounds,

such as palladium chloride (U. S. 2,540,086), potassium choloropalladate (U. S. 2,598,079), etc., or mixtures of such sensitizers; anti-foggants, such as ammonium chloroplatinate (U. S. 2,566,245), ammonumchloroplatinite (U. S. 2,566,263), benzotriazole, nitrobenzimidazole, 5- nitroindazole, benzidinc, mercaptans, etc. (see Mees- The Theory of the Photographic Process, Macmillan Pub., page 460), or mixtures thereof; hardeners, such as i formaldehyde (U. S. 1,763,533), chrome alum (U. S. 1,763,533), glyoxal (U. S. 1,870,354), dibromacrolein (Br. 406,750), etc.; color couplers, such as those described in U. S. Patent 2,423,730, Spence and Carroll U. S. Patent 2,640,776, issued June 2, 1953, etc.; or mixtures of such addenda. Dispersing agents for color couplers, such as those set forth in U. S. Patents 2,322,027 and 2,304,940, can also be employed in the above-described emulsions.

The polymethine dyes represented by Formula I above, which are useful in practicing my invention, can be prepared according to the method described in the copending application Serial No. 585,946, led on even date herewith in the names of L. G. S. Brooker and D. W. Heseltine.

The term lower alkyl as used in the foregoing specication and the following claims means an alkyl group containing from 1 to 2 carbon atoms.

What I claim as my invention and desire secured by Letters Patent of the United States is:

1. A photographic silver halide emulsion sensitized with a supersensitizing combination of at least one dye selected from those represented by the following general formula:

the benzimidazole series, and those of the 3,3dialkyl. indolenine series, and at least one pyridine base selected from those represented by the following general formula:

wherein R4 represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms.

2. A photographic silver halide emulsion as dened in claim 1 wherein the, silver halide is silver-bromiodide and wherein the pyridine base is pyridine.

3. A photographic gelatino-silver-halide developing-out Vemulsion sensitized with a supersensitizing combination of at least one dye selected from those represented by the following general formula:

2 carbon atoms, R1 and R2 each represents a member 9. selected from theY group consisting. of ahydrogenf atom and anvalkyl group. containingffron'i lrto 2tcarbon1atoms; R3 representsv armember selected fromV the-.group consisting of a hydrogen atom' and azcarbalkoxyl .groupacontaining from 2 to 3 carbonatorns, n represents apositive integer of fromfl to 2, and Zrepresents. the nonfmetallicv atoms necessary to complete a heterocyclic. nucleus selected from the groupconsisting ofthose ofthefbenzothiazole series, those of the naphthothiazole series,.those" of the acenaphtholl1,2]thiazoleiseries,..those of-.the -benzoXazole series, those of the naphthoxazole series,v those of the benzoselenazole series, those of the naphthoselenazole series, thosevof the thiazoline series, those of the benzimidazole series, and those of the 3,3-dialkylindolenine series, and at least onepyridinebase` selectedflfrom those represented by the following general formula:

wherein R4 represents a'member selected fromthezgroup consisting of a hydrogenatom andan alkyl-group. containing from 1 to 2 carbon atoms.`

4. A photographic silver halide emulsion@y sensitized with a supersensitizing combination of atleast-'one dye selected from those representedby the following general formula:

wherein R4 represents a member-selectedfrom the group consisting of a hydrogen atom and an alkyl= group containing from 1 to 2 carbon atoms.

5. A photographic gelatino-silver-halide developing-out emulsion sensitized with a supersensitizing combination of a dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from l to 2 carbon atoms, R1 and` Rzeach represents a.member.s'ef lected from the group consisting; of ahydrogen atom..and an alkyl group containing from 1' to 2 carbon atoms, R3 represents a member selected from the group consisting of a hydrogen atom and a carbalkoxyl groupy containing 75A fromi 2 to; 3 carbon; atoms',t. and; Z1 represents the.' none metallici atoms necessaryztcrzcomplete :a heterocyclic nufiv cleus ofthe benzothiazole series, and zupyrirline.;baser selected from those represented. by the following general formula whereinkbrepresents a-:rnember selected vfrom the vgroup consisting of :a hydrogen atomand. anf.. alkyl group. 'conf tainingffrom .1 vto .2,fcarbon atoms.

6. A photographic gelatino-silverfhalide. developing-.out emulsion sensitized with a supersensitizing combination of a dye selected from those represented by the following general formula:

wherein -R represents an `alkyl groupcontaining from-1 to 2 carbon .atoms andZ represents. the non-metallic atoms necessaryto complete` a heterocyclic nucleus of the benzothiazole series, and pyridine. y

7. A photographicv gelatino-silver-halide` developing-out emulsion sensitized `with va 4supersensitizing combination .of`

2[ 3 f- Vdicyanomethylenel-cyclohexene-V 1,-y1 methylene] 3methylbenzothiazoline and pyridine.

8. A photographic gelatino-silver-halide developing-out emulsion sensitized with a supersensitizing combination of a dye selected from thoserepresented by the following wherein R represents an alkyl group containing from 1 to 2 carbon atoms, R3 represents a carbalkoxyl group containing from 2 to 3 carbon atomsand Z represents the non-metallic atomsnecessarytocomplete a heterocyclic nucleus of thetbenzothiazoleseries and pyridine.

9. A photographic gelatino-silverhalide developing-out emulsion sensitized with a supersensitizing combination of 2- 6-carbethoxyS-dicyanomethylenel-cyclohexen- 1- yl)methy1ene] QB-methylbenzothiazoline and pyridine;

10. A. photographic silver halide emulsion sensitizedl with a supersensitizing combinationof at least one dye selected from those representedby*theffollowing general formula:

wherein R represents `an alkylgroup containing from 1 to 2 carbon atoms, R1 and R2, each represents a member selected from the group consi-sting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms, R3 represents a member selected from the group consisting of a hydrogen: atom andxa carbalkoxylrgroup, n representsv a .positive integer. of from 1, to 2, and Z represents. thel non-metallic. atomsnecessary to complete .a heterocyclic.

11 nucleus of the benzoxazole series, and-at least one pyridine base selected from those represented by the following general formula:

wherein R represents an alkyl group containing from 1 to 2 carbon atoms, R1 and R2 each represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2carbon atoms,`

R3 represents a member selected from the group consisting of a hydrogen atom and a carbalkoxyl group con` taining from 2 to 3 carbon atoms, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzoxazole series, anda pyridine base selected from those represented by the following general formula: i

wherein R4 represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from` 1 to 2 carbon atoms.

12. A photographic gelatno-silver-halide developingout emulsion sensitized with a supersensitizing combination of -a dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from 1 wherein R represents an alkyl group containing from 11 to 2 carbon atoms, R3 represents a carbalkoxyl group containing from 2 to 3 carbon atoms, and Z represents 12 the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzoxazole series and pyridine.

15. A photographic gelatino-silver-halide developingout emulsion sensitized with a supersensitzing combination of 2 [(6 carbethoxy 3 dicyanomethylene 1- cyclohexen l yl)methy1ene] 3 methylbenzoxazoline and pyridine.

'16. A photographic silver halide emulsion sensitized with a supersensitizing combination of at least one dye selected from those represented by the following general formula:

wheen'n R represents an alkyl group containing from 1 to 2 carbon atoms, R1 and R2 each represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms, R3 represents a member selected from the group consisting of a hydrogen atom and a carbalkoxyl group, n represents a positive integer of from 1 to 2, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzimidazole series, and at least one pyridine base selected from those represented by the following general formula:

wherein R4 represents `a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms.

17. A photographic gelatino-slver-halide developingout emulsion 4sensitized with a supersensitizing combination of a dye selected from those represented by the following general formula:

wherein R represents an alkyl group containing from l to 2 carbon atoms, R1 and R2 each represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms, R3 represents a member selected from the group consisting of a hydrogen atom and a carbalkoxyl group containing from 2 to 3 carbon atoms, and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the benzimidazole series, and a pyridine base selected from those represented by the following general formula:

wherein R4 represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from I to 2 carbon atoms.

18. A photographic gelatino-silver-halide developingout emulsion. sensitized with a supersensitizing combina- 13 14 tion of a dye selected from those represented by the out emulsion sensitized with a supersensitizing combinafollowing general formula: tion of 2 [(3 dicyanomethylene 5,5 dimethyl 1- H cyclohexen 1 yl)methylene]-l,3dietl1ylbenzimidazoline l ,Z\ C CN and pyridine. R l H o \o-C/ 5 0 0 References Cited in the file of this patent H; /CH CN UNITED STATES PATENTS R1 2,398,778 Canon et a1. Apr. 23, 1946 n 10 2,478,369 Carroll et al. Aug. 9, 1949 wherein R represents an alkyl group containmg from 1 2,697,707 Kendall et a1, Dec, 21, 1954 to 2 carbon atoms, R3 represents a carbalkoxyl group containing from 2 to 3 carbon atoms, and Z represents OTHER REFERENCES i the non-metallic atoms necessary to complete ka hetero- M6652 The TheOfY 0f the PhOtOgFaPhlC PIOCGSS, re-

cyclic nucleus of the benzimidazole series and pyridine. 15 ViSed ed, Mlcmiu'all C0, N- Y, 1954, Pages 376 and 19. A photographic gelatino-silver-halide developing- 415. (Copy 1n Sc1.L1b.) 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION SENSITIZED WITH A SUPERSENSITIZING COMBINATION OF AT LEAST ONE DYE SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 